Natural products are extremely important sources of bioactive compounds for agricultural and pharmaceutical applications. Many of the top selling drugs are natural products or semisynthetic derivatives of natural product leads. Filamentous fungi constitutes a prolific producer of some of the most important drugs known to human kind, including penicillin from Penicillium notatum and the statins from Aspergillus species. Metabolic engineering of industrially important filamentous fungi is therefore an attractive research goal from both scientific and biotechnological perspectives. In this work, we will metabolically and biosynthetically engineer the production of the blockbuster drug simvastatin (Zocor) from Aspergillus terreus. Simvastatin is highly effective in lowering cholesterol levels and is one of the best selling drugs in the world with annual sales exceeding $5 billion. Simvastatin is a semisynthetic drug derived from the natural product lovastatin (Mevacor) and is currently produced using an inefficient and laborious multistep chemical synthesis. Therefore, new methods that can increase the efficiency of simvastatin synthesis, and decrease the cost of production will be of significant impact. In this project, we will perform metabolic engineering of the lovastatin producer A. terreus towards direct biosynthesis of simvastatin. Based on extensive preliminary results, three specific aims will be pursued: Aim 1: Metabolic Engineering of A. terreus for Precursor-Directed Biosynthesis. Aim 2: Optimization of the Precursor-Directed Biosynthesis of Simvastatin. Aim 3: Biosynthetic Pathway Engineering of A. terreus. The proposed research is innovative because metabolic engineering towards the biosynthesis of a blockbuster drug such as simvastatin has not been accomplished. This work will represent an important milestone in applying metabolic engineering and biosynthetic engineering towards the synthesis of a compound as commercially important as simvastatin. Successful outcome of this project will lead to a completely new method of producing simvastatin that is more efficient than the current processes. In addition to the application-driven goal, results from this project will contribute to our fundamental understanding of A. terreus metabolism, protein structure and function, as well as fungal biosynthetic pathways.